In respective mobile telecommunication systems, such as GSM (Global System for Mobile communications) and UMTS (Universal Telecommunication System), operators have the possibility to use SAT (SIM Application Toolkit (SIM=Subscriber Identity Module)) or USAT (USIM Application Toolkit (USIM=UMTS Subscriber Identity Module)) mechanisms in order to define network operator-specific applications. These applications reside on a UICC/SIM card (Universal IC Card; IC: Integrated Circuit) and use certain functionalities of the mobile phone, where the UICC/SIM card is usually plugged in or is otherwise coupled with. Further such details are particularly described in specification documents 3GPP TS 31.111, USIM Application Toolkit (Release 5); 3GPP TS 31.111, USIM Application Toolkit (Release 5); 3GPP TS 23.140, Multimedia Messaging Service (MMS), Functional description, stage 2; 3GPP TS 31.102, Characteristics of the USIM Application (Release 5); and in W. Rankl, W. Effing, Smartcard Handbook, John Wiley & Sons, second edition, 2000.
Mobile communication services such as the 2nd generation (e.g., GSM) and the 3rd generation (e.g., UMTS) use well-defined smart cards in addition to telecommunication devices like mobile phones. Plugged into a telecommunication device like a mobile phone, these smart cards enable a user to use the mobile communication service he/she has subscribed to. Moreover, user preferences and settings, as well as a user's personal information, can be stored on such smart cards. In GSM these cards are called SIM. In UMTS, one distinguishes between the physical card (the UICC) and its logical functionality (the USIM).
CAT/SAT/USAT (Card Application Toolkit/SIM Application Toolkit/USIM application Toolkit) is a toolkit which provides operators with an API (Application Programming Interface), which enables them to put their own, network operator-specific applications on a SIM or a UICC card taking into account the particularities of mobile phones, independent of the particular operator, smart card manufacturer and mobile phone manufacturer. For that purpose, CAT/SAT/USAT provides a standardized execution environment for applications stored on the SIM/USIM/UICC and the ability to utilize certain functions of the supporting mobile equipment, particularly a telecommunication device (below abbreviated by ME ); i.e., the mobile phone. CAT/SAT/USAT provides mechanisms, which allow applications, residing in the UICC/JUSIM/SIM, to interact and operate with any ME which supports the specified mechanism(s), thus ensuring interoperability between a UICC/USIM/SIM and an ME, independent of the respective manufacturers and operators. The UICC/SIM card is the physical basis for this toolkit since UICC/SIM are usually owned by the operator and can, thus, be adapted most easily to the operator's needs. Examples of such USAT mechanisms are the (U)SAT proactive commands (often also called proactive UICC commands) like DISPLAY TEXT, GET INPUT, PLAY TONE, RECEIVE DATA, SEND DATA, SEND SHORT MESSAGE, SET UP CALL, etc, of which applications residing on the USIM/UICC can make use of. Since only the mobile equipment can act as the master in the communication between the ME (mobile equipment) and the UICC/SIM , the proactive (U)SAT commands are defined to create a way for the UICC/SIM to indicate, that the UICC/SIM wants to send a command to the ME. That is, the UICC uses the proactive (U)SAT commands to issue instructions to the ME. The ME knows what action it has to take when it receives this kind of instruction.
Nowadays, in mobile networks like GSM, SMS (Short Message Service) is used to send and receive short messages between mobile terminals. Currently, a new messaging service, the so-called MMS (Multimedia Messaging Service), is being standardized. Contrary to SMS, MMS messages may contain multimedia elements such as for example, text, still image, audio or video. MMS is a peer-to-peer messaging service between two MMS User Agents (or between an MMS User Agent and a 3rd Party Value-Added Service Provider, VASP), which are both connected to an MMS Relay/Server. The MMS User Agent resides either on a mobile phone (e.g., a UMTS-UE (UE abbreviation for User Equipment)) or a GSM-MS (MS abbreviation for Mobile Station), on an external device; for example, a notebook/laptop, coupled or connected to a mobile phone, or even on a PC or other telecommunication devices not connected or not coupled to a mobile phone. It is an application layer function on the respective telecommunication equipment that provides the user with the ability to view, compose and handle the Multimedia Messages (below abbreviated by MMs), including submission and reception of MMs. A MMS Relay/Server is a network entity responsible for the storage and handling of incoming and outgoing messages and for the transfer of the message between different messaging systems.
To summarize, the Multimedia Messaging Service (MMS) is a new messaging service, with which messages with multimedia elements of different types (e.g. still image, audio, video) and different formats (with respect to still image: e.g., JPEG or GIF) can be exchanged between (especially mobile) terminals via network components or directly with each other.